4. In a chocolate factory, milk chocolate bar with caramel filling is made by coating the melting chocolate (50C) on the surface of cylindrically shaped caramel bar in a square channel, as shown in figure 2 with the shape factor indicated in the figure. The length of the channel is 1m. The melting point of caramel is >100C. The temperature of the caramel is initially the same as that of the melting chocolate. After the coating is completely done, the surface of the chocolate is suddenly quenched to 5C to temper the chocolate layer and is maintained at this temperature during the tempering process. The temperature at which milk chocolate solidifies is 30C. Determine the time required to completely solidify the chocolate bar before so that it can be cut into smaller pieces for packing. State your assumptions clearly. Table 1 (20 marks)